THE GENUS DENDROCTONUS. 



35 



ventral angle or ventral section of the postepimerum, which might 

 be mistaken for a postepisternum, is indicated by the pleural apodeme 

 and pleural suture which here join the dorsal angle of the coxa. It 

 is not impossible, however, that this plate may represent a combined 

 postepisternum and postepimerum. 



METASTERNA. 



The metasterna (figs, 2, 3) form a broad rectangular plate separated 

 into two lateral sections by a median longitudinal line. The pre- 

 sternum and poststernellum are not represented by external parts. 



Spiracle 1 

 -Epipleuriie 1 



- Spiracln2 

 ~ Epipleurite 2 

 0_- f- - -Spiracles 

 V V - - 1 - Epipleurite 3 



Spiracle 4 

 'Epipleurite 4 



- f Spiracle 5 



"^Epipleurite 5 



- Spiracle 6 

 Epipleurite 6 



Propygidium 



' - Spiracle 7 

 Epipleurite 7 



Pyffidium 



Stridulaling scraper 



Fig. 22. — Dendroctonus miens: Abdominal tergites. a, Anterior arm of epipleurite 7; 6, posterior arm of 

 epipleurite 7; c, membranous lobes. (Original.) 



Sternum. — The sternum is evidently represented by the large con- 

 tinuous area between the mesocoxse and the small median plate and 

 the slightly acclivous area anterior to the metacoxa. 



Sternellum. — The sternellum is evidently represented by the pos- 

 terior median plate and the posterior acclivous areas (fig. 2, a). The 

 relation of the latter to the sternellar area is indicated by the attach- 

 ment of the posterior pair of clavicular muscles. 



THE ABDOMEN. 



The abdominal terga, pleura, and sterna, and their relative pro- 

 portions, are shown in figures 1-3 and 22-25. 



79980—09 4 



